The effects of scalar and pseudoscalar ultralight bosonic dark matter (UBDM) were searched for by comparing the frequency of a quartz oscillator to that of a hyperfine-structure transition in ${}^{87}\mathrm{Rb}$, and an electronic transition in ${}^{164}\mathrm{Dy}$. We constrain linear interactions between a scalar UBDM field and standard-model (SM) fields for an underlying UBDM particle mass in the range $1\times {10}^{-17}–8.3\times {10}^{-13}\mathrm{eV}$ and quadratic interactions between a pseudoscalar UBDM field and SM fields in the range $5\times {10}^{-18}–4.1\times {10}^{-13}\mathrm{eV}$. Within regions of the respective ranges, our constraints on linear interactions significantly improve on results from previous, direct searches for oscillations in atomic parameters, while constraints on quadratic interactions surpass limits imposed by such direct searches as well as by astrophysical observations.

We present a search for fundamental constant oscillations in the range 20 kHz–100 MHz that may arise within models for ultralight dark matter (UDM). Using two independent optical-spectroscopy apparatuses, we achieve up to $\times 1000$ greater sensitivity in the search relative to previous work [D. Antypas et al., Phys. Rev. Lett. 123, 141102 (2019).]. We report no observation of UDM and thus constrain respective couplings to electrons and photons within the investigated UDM particle mass range $8\times {10}^{-11}–4\times {10}^{-7}\mathrm{eV}$. The constraints significantly exceed previously set bounds from atomic spectroscopy and, as we show, may surpass in future experiments those provided by equivalence-principle (EP) experiments in a specific case regarding the combination of UDM couplings probed by the EP experiments.

Sensitive and accurate diagnostic technologies with magnetic sensors are of great importance for identifying and localizing defects of rechargeable solid batteries using noninvasive detection. We demonstrate a microwave-free alternating current (AC) magnetometry method with negatively charged NV centers in diamond based on a cross-relaxation feature between nitrogen-vacancy (NV) centers and individual substitutional nitrogen (P1) centers occurring at 51.2 mT. We apply the technique to non-destructively image solid-state batteries. By detecting the eddy-current-induced magnetic field of the battery, we distinguish a defect on the external electrode and identify structural anomalies within the battery body. The achieved spatial resolution is μμμ$360\mathsf{\mu }\mathrm{m}$. The maximum magnetic field and phase shift generated by the battery at the modulation frequency of 5 kHz are estimated as 0.04 mT and 0.03 rad respectively.

Spin-exchange relaxation-free (SERF) atomic magnetometers seem to be the state-of-the-art magnetic sensors today as they have achieved a sensitivity of femtotesla in the elimination of broadening contribution of spin-exchange collisions operated in the mode of SERF regime. In order to extend the practicability of SERF atomic magnetometry in superb performances in a movable platform, ensuring and testing the working status of alkali atoms are of great importance. Given the fact that in the premise of SERF regime, the linewidth of magnetic resonance would be narrowing down and the precession frequency would become a constant fractional value of the Larmor frequency for alkali atoms, we measure the gyromagnetic ratio of weakly polarized alkali-metal vapor by yielding the damped oscillating curves and fitting measured increments of frequency and magnetic field to identify the working regime of alkali atoms in a fast and straightforward manner. The experimental results have good agreements with theoretical analysis and simulation, and the whole measurement process lasts milliseconds with relatively measured error ± 1% in the temperature range of T = 156 °C-184 °C. To testify the validity of the innovation, magnetic resonance line is obtained in the same condition proffering the width comparative with the outcome from simulation, indicating the spin-exchange broadening has been eliminated, presenting the same conclusion with innovation, and providing systematic sensitivity 30 fT/Hz1/2.

This paper aims to explore the detection defect of residence times difference (RTD) fluxgate working in low-power mode and present the countermeasures for sensor resolution improvement and linearity enhancement. The main defects are amplitude and symmetry changes induced in the output spikes of fluxgate probe due to the magnetic field. These defects lead to thresholds deviation and asymmetry, then cause severe performance degradation especially on detection resolution and linearity according to the RTD theory. To overcome such effects, the optimized RTD method based on voltage extraction and feedback technology is proposed to implement magnetic field compensation and achieve a zero-field running regime of the RTD fluxgate. In this regard, the sensor linearity is improved by a factor of 38, and the resolution degradation effect is suppressed more than 6 times, verified by the laboratory experiments. The optimized detection method proposed in this paper demonstrated a great potential to achieve lower power consumption and will make the RTD fluxgate more promising technology among bio-magnetic applications.

Plenty of multimedia contents such as traffic images, surveillance video, music and movie will flood into vehicular ad hoc networks. However, content distribution over VANETs is not a easy task, due to the high mobility of vehicles and intermittent connectivity. Infrastructure-based scheme can relieve the problem, but with a large amount of investment. In this paper, we propose a mobile content distribution scheme based on roadside parking cloud (RPC), which is formed by the parked car on the roadside, and mobile cloud (MC), which is formed by moving cars on the road. According to a trip history model, a mobile car can estimate its following trajectory. When it wants to download the content, gateway node of the RPC will work out a downloading schedule, which tells it how much chunks it can download from which RPCs. Moreover, the helper of the mobile car in mobile cloud would deliver specified chunks to it when there is lack of RPC in the following trip. Simulation results show that cloud-based scheme performs better than inter-vehicle communication approach and cluster-based scheme.